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In select patients when transplant is not possible, liver surgery is a preferred treatment for liver cancer and is performed with curative intent. Currently, only about 20% of patients are eligible for resection due to the complexity of the procedure. Image-Guided Liver Surgery (IGLS) that utilizes preoperative Computed Tomographic imaging (CT) data is not yet standard of care, and one of the confounding factors toward its realization in the liver is the presence of soft-tissue deformations that compromise the fidelity of these systems. IGLS systems involve intraoperative data collection to achieve image-to-physical alignments, and realizations to date have previously used an optically tracked stylus that requires physical contact with the liver. One source of error in this process involves contact pressure that may cause inaccuracies during the acquisition of liver shape data. In this study, we use a non-contact Conoprobe digitization method for comparison against stylus-based acquisition. We developed a novel Conoprobe device attachment and sterilization process to enable prospective data acquisition in the operating room. The goal of this work is to study the difference between rigid registration and non-rigid registration with respect to two forms of digitization (contact and non-contact) in vivo. For this preliminary work, data from one patient undergoing liver resection was analyzed from our novel prototype under an IRB approved study at Memorial Sloan Kettering Cancer Center. The organ surface coverage of the two digitization methods was compared. Rigid and model-based non-rigid registration were performed and evaluated for a patient undergoing liver surgery. Segmented contours of the ultrasound-identified targets were compared to their registered preoperative counterparts for accuracy validation. The findings indicate that surface coverage of the Conoprobe is less than that of stylus, suggesting that non-contact accuracy benefits may be obscured by inferior data coverage. However, more investigation is needed to potentially increase Conoprobe surface data extent during acquisition.
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